[C320-list] Auto-Prop Issues

[Robert E. Sloat]

Gil-When I ordered my Autoprop from AB they asked for a bunch of information
including my engine model and transmission gear ratio.  The propeller I got
works fine and gets me to maximum rpm.  I am in southern Lake Michigan and a
little fouling on the propeller last season caused the maximum rpm to drop
by 400 rpms.  A simple hand cleaning cleared up the problem.

One point they don't tell you is that you may have to put an extension
spacer (I believe mine was 5/8") on your shaft to allow the blade to clear
the strut when it reverses.  I got mine from Spurs Marine in Florida.  The
other approach is to cut a notch in the strut to allow clearance.  The
hardest part of using the extension spacer is getting the exact thickness of
the spacer so the propeller hub stays within 11/2" of the strut to reduce
potential vibration while still clearing the strut.

Below is at note I sent to the C320 site on November 9, 2007.  You can look 
in the forums and search for autoprop and find a number of interesting items 
on Autoprop, include someone who brought a boat where the previous owner had 
installed an Autoprop 21/2" back of the strut and got vibration.  A good 
product inproperly installed.

"November 9, 2007

I have one full season on my AutoProp and no shaft problems. The front hub 
of the AutoProp is about 1.5 inches aft of the strut and the blades clear 
the strut by about 1/8 inch. I chose not to do the notch in the strut, but 
instead purchased a spacer from Spurs marine in Florida to get to 1.5 inch 
spacing for blade clearance. The spacer fits in the coupling at the front of 
the propeller shaft where it connects to the transmission output.

It took a little engineering measurements to determine the spacer thickness 
I needed (5/8 inch) to get me to blade clearance to both clear the strut and 
keep the distance from the strut to the front of the propeller hub to 1.5 
inches or less. This will vary depending on the spacing from your OEM 
propeller to the strut when the boat was built.

The rule of thumb per AB Marine, from whom I bought the AutoProp, is that 
the propeller should be no further than 1.5 inches from the strut to 
minimize shaft flexing. 2 1/2 inches between the strut and the front of the 
propeller hub is too far and probably causes shaft flexing."

Bob Sloat
Savannan Hull 894


----- Original Message ----- 
From: "Richard A. Walker" <dickwalker at att.net>
To: <C320-List at Catalina320.com>
Sent: Sunday, April 06, 2008 12:29 PM
Subject: Re: [C320-list] Auto-Prop Issues


Gil,

You need to look at the transmission and get the reduction gear reading.

Yes but easily fixed.  Perhaps you could give me your email address.  Also
easer to call me.

Cheers,

Dick Walker
C-320 (687) WindWalker II
740 Olive Ave.
Coronado, CA 92118-2136
619.435.8986

-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of
Niedobre at aol.com
Sent: Sunday, April 06, 2008 8:47 AM
To: C320-List at catalina320.org
Subject: [C320-list] Auto-Prop Issues

Has anyone had issues regarding the incorrect sizing of the Autoprop from
AB
Marine?  What did they do about it?
Gil   s/v Amara



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